On Jul 5, 2006, at 4:41 PM, Stephen Farrell wrote:
Douglas Otis wrote:
On Jul 5, 2006, at 2:36 PM, Paul Hoffman wrote:
At 12:44 PM -0700 7/5/06, Douglas Otis wrote:
DKIM generally represents a domain wide entity. A trusted third
party (TTP) establishes trust between two parties when both
trust the third party. For DKIM, the TTP would be the signing
domain verified by DNS.
This is completely wrong, and goes against nearly everything that
this WG has been working on. The signing domain is *not* trusted.
Does anyone other than Doug think that it is?
You have misunderstood what was being said.
Clash of terms there. The DNS, as used by DKIM, is a TTP in
crypto-protocol terms according to the well-understood use of that
term [1]. I think I first heard such a definition 20 years ago.
From your reference:
---
In cryptography, a trusted third party (TTP) is an entity which
facilitates interactions between two parties who both trust the third
party; they use this trust to secure their own interactions. TTPs are
common in cryptographic protocols, for example, a certificate
authority (CA).
---
While DNS associates a key with a domain name, there should be no
expectation this domain name represents a tangible entity or offers
meaningful recourse. There are thousands of entities involved in
these associations, where the basis is often limited to just the
domain name itself. It is difficult to consider an amalgam of often
anonymous entities a "trusted third party" for "securing" email
interactions. Use of DNS by DKIM certainly falls short of the
expectations of a TTP as set by Certificate Authorities or the
example given of a notary public. For DKIM to offer security, a
separate assessment of the DKIM domain name should be made (likely by
a TTP). In that sense of trust or "securing" interactions, DNS fails
this definition of TTP for email in my view.
-Doug
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